At present, a fuel cell system including a fuel cell that receives supply of a reactant gas (a fuel gas and an oxidizing gas) to generate power has been proposed and put to practical use. Such a fuel cell system is provided with a fuel supply channel for introducing the fuel gas to be supplied from a fuel supply source such as a hydrogen tank into the fuel cell.
Meanwhile, a pressure adjustment valve (a regulator) which reduces a supply pressure to a certain value is generally disposed along a fuel supply channel, when the supply pressure of the fuel gas from the fuel supply source is remarkably high. In recent years, a technology is proposed in which a mechanical variable pressure adjustment valve (a variable regulator) for changing the supply pressure of the fuel gas in, for example, two stages is disposed along the fuel supply channel, whereby the supply pressure of the fuel gas is changed based on an operation state of the system (e.g., see Japanese Patent Application Laid-Open JP2004-139984A).